The present disclosure relates to a laser scanning device including a rotary polygon mirror, an image forming apparatus including a laser scanning device, and a reflection surface identification method executed in a laser scanning device.
In an electrophotographic image forming apparatus, such as a printer, for forming an image, light emitted from a light source based on image data is scanned over a photoconductor drum by a rotary polygon mirror, and an electrostatic latent image corresponding to the image data is formed on the photoconductor drum. In this type of image forming apparatus, a light emission timing corresponding to each line of image data, namely, an electrostatic latent image writing timing is determined based on a light detection timing at which the light emitted from the light source and scanned by the rotary polygon mirror is detected by a light detecting portion.
In addition, there is known a conventional technique configured to identify a reflection surface of the rotary polygon mirror based on the light detection timing at which the light is detected by the light detecting portion, and an output timing at which a drive signal that is to be input to a drive motor first after the detection timing, is output. Specifically, it is monitored in each of predetermined division periods in a light detection cycle of the light detecting portion whether or not the drive signal is output, and the reflection surface of the polygon mirror is identified based on whether or not output of the drive signal was detected in a certain division period that corresponds to a certain reflection surface, or in any of division periods before and after the certain division period. This makes it possible to identify a reflection surface of the polygon mirror even in a case where the interval between the light detection timing detected by the light detecting portion and the drive signal output timing has been shifted due to environmental variations.